The present invention relates to a suspension type elevator system having a flat belt support.
Suspension type elevator systems usually comprise an elevator car and a counterweight, which are movable in an elevator shaft or along freestanding guide devices. For producing the movement the elevator system comprises at least one drive with at least one drive pulley, which supports, by way of support and drive means the elevator car and the counterweight and transmits thereto the necessary drive forces.
The support and the drive means are termed support means in the following descriptions.
Distinction is made between elevator systems in which steel cables with a round cross-section are used as support means and more modern elevator systems that have a flat, belt-like support means.
An elevator system with a flat-belt-like support means in different arrangements is shown from PCT Patent Application WO 99/43593. The elevator according to this patent application comprises a drive motor which is arranged in the shaft space above the elevator car and so acts by way of least one drive pulley on the variously arranged flat support means disposed in operative connection with the elevator car that the elevator car is moved upwardly and downwardly. In order to halve the tensile force arising in the support means and the traction force required at the drive pulley, in some of the disclosed arrangements of the support means the suspensions of elevator car and counterweight are executed as a 2:1 suspension system.
By the expression 2:1 suspension system, there is understood a system in which support means driven by way of a drive pulley move a elevator car and/or a counterweight, wherein the support means are so arranged that the section thereof disposed in contact with the drive pulley moves twice as fast as the elevator car and/or the counterweight. The support means in that case are so arranged that they loop around at least one drive pulley and at least one respective deflecting roller at each of the elevator car and counterweight and that they are fixed at their ends in the upper region of the elevator shaft.
Additional deflecting or diverting rollers are required in all variants, which are illustrated in the published WO 99/43593, with a 2:1 suspension system.
In the interests of optimum utilization of space and the use of drive motors with minimum drive torque, the drive pulley and also the deflecting or diverting rollers have smallest possible diameters.
Experience with elevator installations of that kind has shown that expectations with respect to the service life of the support means employed are not fulfilled, i.e. due to arising material defects these often have to be replaced prematurely, this evidently being attributable to loading of the support means in bending.